Symptoms, Carcinogens, and Oncogenic Viruses

What are some symptoms of cancer?

Depending upon the type of cancer a patient has, they could exhibit
various symptoms. The American Cancer Society has
developed a general list of seven symptoms that could be warning
signs of cancer :

unusual bleeding or discharge (cancers of the ovaries or of
the uterus)

a lump that does not go away (cancer of the breast)

a sore that does not heal within two weeks (cancers of the
mouth)

change in bowel or bladder habits (cancer of the colon or
rectum)

persistent hoarseness or cough (cancer of the lung)

indigestion or difficulty swallowing (cancers of the esophagus
or head and neck)

change in a wart or mole (cancers of the skin)

What causes cancer?

Epidemiological Studies

Epidemiological studies are studies of cancer looking at various
factors such as diet, race, age, and environment. These studies
show that there are numerous factors that contribute to a patient
being diagnosed with cancer. Two such factors are carcinogens
and oncogenic viruses.

Carcinogens

Carcinogens are substances known to cause and/or promote cancer.
Carcinogens can be either man-made, such as cigarette smoke, or
present naturally in the environment, as is ultraviolet radiation
from the sun, both of which are known to play a major role in
the development of cancer. Carcinogens can also enhance other
factors that cause the cancer. Certain cancers develop slowly.
It can take from 5 to 40 years for cancer to develop after exposure
to a cancer-causing agent, making identification of carcinogens
difficult. The number of exposures as well as the length of time
exposed to carcinogens determine whether a cancer will develop,
but there is no evidence that there is a "safe" level
of any carcinogen. Some known carcinogens are:

arsenic and some arsenic compounds (cancers of the lung)

asbestos (cancers of the lung)

benzene- a chemical used in the manufacture of plastics, paints,
and adhesives also found in exhausts from cars and cigarette smoke
(cancer of the bladder)

anti-cancer drugs

vinyl chloride

tobacco (cancers of the lung, esophagus, and/or mouth)

alcohol (cancers of the pancreas, head and neck, and/or liver)

Oncogenic viruses

These are pictures from the BRCA1 lab. Scientists work here studying the gene which is thought to cause breast cancer.

Oncogenes are genes within a cell that may initiate the cells'
transformation from normal to malignant. Some known oncogenes
are the BRCA 1 gene which is linked to breast cancer or the gene
linked to colon cancer. Oncogenic viruses are
viruses that are linked to cancer. There have been almost 40 oncogenic
viruses discovered including HIV, HPV (Human Papilloma Viruses),
herpes viruses, hepatitis B and C viruses, and retroviruses. Researchers
have found that the immune system may recognize the difference
between healthy cells and cancer cells and eliminate those that
become cancerous. Cancer may develop when the immune system breaks
down or is overwhelmed. This may account for the link between
HIV and cancer.